Workshop “Multiple Faces of Interstellar Dust” Abstracts ...lana/DUST2016/... · Interstellar dust revealed through X-ray spectroscopy Elisa Costantini 1 , Cor de Vries 1 , Sascha

Workshop “Multiple Faces of Interstellar Dust”

September 13-16, 2016, Garching

Abstracts of oral contributions

1. Properties of local dust Invited Talk: Interstellar Amorphous Silicates: Prolate vs. Oblate, Porous vs. Dense Bruce T Draine1, Brandon S. Hensley2 1Princeton University, Princeton, NJ, USA 2Jet Propulsion Laboratory, Pasadena, CA, USA By modeling the observed extincton and polarization in the vicinity of the 9.7um and 18um silicate resonances, we constrain the shape and porosity of the grains containing interstellar silicate material. The silicate-bearing grains tend to be flattened, e.g., oblate spheroids with axial ratio > 1.5. We also consider various possible continuous shape distributions, and find that the Ossenkopf-Henning-Mathis (1992) continuous distribution of ellipsoids is consistent with the data. The fits to the observations favor low porosity for the grains. The observed polarization of the 10um feature, and the polarized far-infrared and submm emission observed by Planck, require only moderate alignment of the silicate-bearing grains. Interstellar dust revealed through X-ray spectroscopy Elisa Costantini1, Cor de Vries1, Sascha Zeegers1,2, Harald Mutschke3

1SRON, Netherlands Institute for Space Research, Utrecht, The Netherlands 2Leiden University, Leiden, The Netherlands 3Friedrich-Schiller-Universität Jena, Jena, Germany

In this talk I will show how X-ray high-resolution spectroscopy is a powerful tool to study the chemical composition, crystallinity, depletion, abundances and size distribution of interstellar dust. Extinction by dust produces narrow absorption and scattering spectral features that are detectable by both present and future X-ray observatories (e.g. Decourchelle, Costantini et al. 2013). Recently we performed a large laboratory campaign to measure absorption profiles of dust-analogues. These are essential in interpreting high-quality astronomical X-ray data (Costantini et al. 2013). This synergy between astronomical and laboratory data is a real breakthrough to study silicates in the ISM, by virtue of the O, Fe, Mg and Si features imprinted in the low-energy X-ray band (Costantini et al. 2012, Zeegers, Costantini et al. 2016, subm,). I will also show how future X-ray facilities will be key in determining the dust inclusion of lower abundance elements, like e.g. S and Ca, and to investigate high density environments in the region of the galactic center, rich of molecular clouds. Highlight Talk: Contemporary Interstellar Dust Measured by Cassini: A Chemically Homogenised Population M. Trieloff1, N. Altobelli2, F. Postberg1,3, K. Fiege1, R. Srama3 1Institut für Geowissenschaften, Klaus-Tschira-Labor für Kosmochemie, Universität Heidelberg 2ESA-ESAC, Madrid, Spain 3 Universität Stuttgart, Germany In 1992 the Ulysses spacecraft detected a stream of interstellar dust (ISD) grains passing our solar system [1]. In-situ analyses of the Cosmic Dust Analyser on-board the Cassini spacecraft obtained between 2004 and 2013 yielded the first mass spectra of grains from the Local Interstellar Cloud (LIC) [2]. These 36 interstellar grains can be clearly identified and distinguished from Saturn bound dust by their direction and high velocity, and their mean mass is consistent with the typical ISD size inferred from astronomical observations [2]. Surprisingly, each grain contains the major rock forming elements (Mg, Si, Fe, Ca) in roughly cosmic abundances, with only small grain-to-grain variations. Hence, compositional homogeneity extends down to small spatial scales of 100 nm. In this size regime, neither carbon rich grains (graphite, SiC) nor pure metal nor oxide grains were detected, which sets an upper limit of 8% at the 2 sigma confidence level for these grain species [2]. This finding is in contrast with the isotopically and compositionally diverse populations of circumstellar dust inherited from AGB Stars and supernovae, which typically consist of silicates (e.g., olivine, pyroxene), with minor contributions (few %) of oxides (e.g., corundum, hibonite) and carbonaceous grains, mainly silicon carbide (40) with an abundance of >20%, possibly up to 50%. Moreover, the LIC-ISD grains detected by Cassini also differ in elemental composition, specifically, their variation of Mg/Si, Mg/Fe is significantly smaller. A more homogeneous composition can be explained by destruction, recondensation and

equilibration processes in the ISM that homogenise an initially diverse population that started as circumstellar dust. This is supported by astronomical observations of the diffuse ISM demonstrating that the most condensable elements (atomic mass >23) are depleted in the gas phase and hence bound in solids, while the lifetime of interstellar grains against destruction by supernova shocks of about 0.5 Ga is much shorter than the average residence time of matter in the ISM of 2.5 Ga [3]. References: [1] E. Grün et al., Nature 362, 428-430 (1993). [2] N. Altobelli, F. Postberg, K. Fiege, M. Trieloff et al. Science 352, 312 (2016). [3] S. Zhukovska, H.-P. Gail, M. Trieloff, Astron. Astrophys. 479, 453 (2008). Invited Talk: Fitting extinction and polarization spectra of the diffuse ISM R. Siebenmorgen1, N.V. Voshchinnikov2, S. Bagnulo3, and N. Cox4

1ESO, Garching, Germany, 2Sobolev Astronomical Inst., Russia, St. Petersburg, 3Armagh Observatory, College Hill, UK, 4Universit\'e de Toulouse, UPS-OMP, IRAP, 31028, Toulouse, France, and CNRS, IRAP, 9 Av. colonel Roche, BP 44346, F-31028 Toulouse, France.

We present a model for the diffuse interstellar dust that explains the observed wavelength-dependence of extinction and linear polarisation of light. The model is set-up with a small number of parameters. It consists of a mixture of amorphous carbon and silicate grains with sizes from the molecular domain of 0.5 nm up to about 900 nm. Dust grains with radii larger than 6nm are spheroids. In the presence of a magnetic field, spheroids may be partly aligned and polarise light. We find that the polarization-spectra help to determine the upper particle radius of the otherwise rather unconstrained dust size distribution. Stochastically heated small grains of graphite, silicates and polycyclic aromatic hydrocarbons (PAHs) are included. For each dust component its relative weight is specified, so that absolute element abundances are not direct input parameters. The dust model is confronted against seven FORS polarization spectra of stars along lines-of-sights towards Sco OB1. They are taken within the ongoing Large Interstellar Polarization Survey at the VLT. For these sight lines UV extinction properties are known from IUE. The wavelength-dependence of extinction and linear polarisation are fit simultaneously by the dust model. This will allow deriving typical parameters of the dust in the diffuse ISM. We find that prolate rather than oblate grains gives a better fit to the observed spectra; the axial ratio of the spheroids is typically two and aligned silicates are the dominant contributor to the polarisation. The polarisation spectra are fit introducing a minimum radius of particles of ~100 nm that are aligned. Models that include small grains better fit extinction and spectro-poarisation data than those ignoring them.

Highlight talk: Crystalline silicates in the interstellar medium and envelopes of YSOs Christopher M. Wright1, Tho Do Duy1,2

1School of Physical, Environmental & Mathematical Sciences, UNSW Canberra at the Australian Defence Force Academy, PO Box 7916, Canberra BC 2610, Australia

2Department of Physics, International University – Vietnam National University HCM, Block 6, Linh Trung, Thu Duc, Ho Chi Minh City, Viet Nam

Crystalline silicates are relatively abundant – up to 10-15% by mass – in dust factories and dust repositories. These are respectively outflows from oxygen-rich evolved stars where silicates condense directly out of the gas-phase, and potentially planet-forming disks around young stars, e.g. 1-10 Myr old T Tauri and Herbig Ae-Be stars, where the crystallinity is thought to result from annealing of initially amorphous silicates. However, little evidence has been presented for crystalline silicates in environments where dust resides – the interstellar medium (ISM) and molecular clouds – between production and deposition stages. A few instances have been reported of crystalline silicate absorption bands in envelopes of embedded Young Stellar Objects (YSOs). But up to now these have been considered as special cases, and it is generally thought that silicates in these environments are amorphous. This had been supported by the non-detection by several authors of crystalline silicates in the ISM, including the much cited paper of Kemper et al. (2004, ApJ, 609, 826) titled “The absence of crystalline silicates in the diffuse interstellar medium”. Indeed, physical mechanisms thought to occur in the ISM have led to the expectation that any crystalline silicates ejected into the ISM by their stellar factories would relatively quickly be amorphised. However, we have recently shown that the ISM does contain crystalline silicates, evidenced by absorption bands at 11.1, 11.9 and 23.5 µm detected along several paths toward the Galactic Centre (Wright et al. 2016, MNRAS, 457, 1593), including the same path used in Kemper et al. The crystalline mass fraction is at least 1.5%. Here we present yet further evidence that the ISM – including both diffuse and dense cloud sightlines – as well as YSO envelopes contain readily measurable quantities of crystalline silicates, essentially ubiquitously so in the latter case. Implications for the cosmic dust life-cycle will be discussed.

Crystalline silicates in external galaxies Kemper Ciska1, de Looze Ilse2,3, Baes Maarten3, Camps Peter3, Min Michiel4,5 1Academia Sinica, Institute of Astronomy & Astrophysics, Taipei, Taiwan

2Department of Physics and Astronomy, University College London, UK

3Sterrenkundig Observatorium, Universiteit Gent, Belgium

4SRON Netherlands Institute for Space Research, Utrecht, The Netherlands

5Anton Pannekoek Institute for Astronomy, University of Amsterdam, The Netherlands

Observational evidence has long supported that most of the interstellar silicates in galaxies are amorphous. While crystalline silicates may form around evolved stars at temperatures sufficiently high to allow for annealing, it is thought that the harsh interstellar environment quickly amorphitizes any crystalline silicates, most likely through bombardment by the heavy ions in cosmic rays (Demyk et al. 2001; Jäger et al. 2003; Brucato et al. 2004; Bringa et al. 2007; Szenes et al. 2010), and a firm upper limit of 2% on the crystalline fraction of silicates was derived based on the absence of substructure in the 9.7 µm feature (Kemper et al. 2004; Kemper et al. 2005).

The first detection of crystalline silicates in external galaxies was reported by Spoon et al. (2006) in 12 out of a sample of 77 starbursting Ultraluminous Infrared Galaxies (ULIRGs), with later detections of further galaxies reported by Roussel et al. (2006), Willett et al. (2011), Stierwalt et al. (2014), and Aller et al. (2012). The only one of these studies quantifying the crystalline fraction is the work by Spoon et al. (2006), who report a crystalline fraction of 6-13% in the interstellar silicate reservoirs. A very simple model of the production of crystalline silicate dust by evolved stars, at a level of 10-20% of the total silicate dust production by these stars, is able to explain the observed crystallinities at about 30 Myr after the start of a starburst (Kemper et al. 2011). In general, the model can be used to estimate the transition time and interstellar conditions, such as cosmic ray fluence, based on observational constraints on the crystalline fraction.

However, the small number of known interstellar crystalline silicate fractions in star-forming galaxies limits the usefulness of such a model. We have devised a method to measure the crystalline fraction of silicates in a large number of galaxies quickly and easily. For this purpose, we are performing radiative transfer models of starburst galaxies, with varying crystalline fractions of their interstellar silicates using the SKIRT radiative transfer code (Camps & Baes 2015), and identified a method to determine the crystallinity of silicates in starburst galaxies directly from (archival) infrared spectroscopy.

Chemical composition of cosmic dust in the solar vicinity Maria-Fernanda Nieva1, Norbert Przybilla1 1 Institute for Astro- and Particle Physics, University of Innsbruck, Austria. We have derived the amount of metals incorporated into cosmic dust indirectly, via the comparison of the ISM-gas-phase abundances and our cosmic abundance standard (CAS) derived from a representative sample of early B-type stars in the solar neighbourhood (Nieva & Przybilla 2008, 2012, Przybilla et al. 2008), which is unprecedented in precision and accuracy. Overall, the results indicate a silicate/oxide-

rich and relatively carbon-poor composition of the local ISM dust-phase. Moreover, a comparison of the CAS with gas-phase abundances in the Orion nebula implies that the HII region is devoid of carbonaceous dust. Our results imply that amorphous carbon dust grains are either efficiently destroyed inside the ionized region, or they were a minority species initially as well. The combined evidence from abundances in the ISM and the Orion HII region indicates that dust models considering silicates, PAHs, organic refractory material and possible amorphous carbon, but not graphite, should be investigated more closely. Recently, Altobelli et al. (2016) used the dust analyzer on the Cassini probe to detect 36 interstellar dust grains. They find that, remarkably, these grains lack carbon-bearing compounds and have been homogenized in the interstellar medium into silicates with iron inclusions: Mg/Si, Fe/Si, Mg/Fe, and Ca/Fe ratios are on average CI chondritic (carbonaceous chondrite whose composition is considered as a proxy cosmic element abundances) and agree with the composition inferred by us. This first direct measurement of the chemical composition of interstellar dust grains confirm the robustness of our Cosmic Abundance Standard.

2. Evidence of dust evolution

Invited Talk:

Variations in dust properties from diffuse to dense ISM Ysard Nathalie1, Jones Anthony1, Koehler Melanie2 1Institut d’Astrophysique Spatiale, UMR8617, CNRS/Univ. Paris Sud, Orsay, France 2School of Physics and Astronomy, Queen Mary University of London, London, UK What are the properties of dust in the interstellar medium (ISM) and how do they change depending on local density? Since dust properties influence, for example, the formation and temperature of the major molecules in dense clouds and the grain dynamical behaviour when forming stars and protoplanetary disks, it is important to characterise the grain size, structure, shape, and material composition in all phases of the ISM. Dust spectral energy distributions (SEDs) of dense ISM clouds show a decrease in colour temperature, and an increase in spectral index and opacity in the far-IR and sub-mm [e.g. 1, 2]. These variations cannot be explained with environmental differences alone, but are assumed to occur due to changes in the dust properties [3]. Some of these clouds are also bright at visible to mid-IR wavelengths [e.g. 4, 5, 6]. Recently, Planck-HFI data revealed that dust properties do not change only in the transition from diffuse to dense ISM but also inside the diffuse ISM itself [7], which was considered rather homogeneous until then. Observations by Planck-HFI for NH < 2.5*1020 H/cm20

show variations in the dust temperature, submm opacity, and far-IR spectral index, at constant luminosity. This finding has a great impact on our understanding of the diffuse ISM since it implies that the dust properties vary. In the context of THEMIS (The Heterogeneous Evolution dust Model of Interstellar Solids), a recent core-mantle dust model [8, 9], we show that all observations of the dense ISM can be rather well explained by accretion and coagulation processes [10, 11], whereas variations in grain mantle thickness and size distribution can account for the variations observed in the diffuse ISM [12]. [1] Juvela et al., A&A 527, 111 (2011) [2] Roy et al., ApJ 763, 55 (2013) [3] Ysard et al., A&A 559, 133 (2013) [4] Mattila, A&A 8, 273 (1970) [5] Witt et al., ApJ 427, 227 (1994) [6] Steinacker et al., A&A 511, A9 (2010) [7] Planck Collaboration XI, A&A 571, A11 (2014) [8] Jones et al., A&A 558, 62 (2013) [9] Koehler et al., A&A 565, 9 (2014) [10] Koehler et al., A&A 579, 15 (2015) [11] Ysard et al., A&A 588, 44 (2016) [12] Ysard et al., A&A 577, 110 (2015) Characterizing Dust in Dense Interstellar Environments using the Si K-edge Sascha Zeegers1,3, Elisa Costantini1, Cor de Vries1, Harald Mutschke2 , Alexander Tielens3 1SRON, Utrecht, The Netherlands

2Astrophysikalisches Institut und Universitäts-Sternwarte (AIU), Jena, Germany

3Leiden Observatory, Leiden, The Netherlands

Bright X-ray binaries, distributed along the Galactic Plane, can be used as background sources to probe intervening dust along several sight lines. The interstellar dust is characterized by studying the shape and observed energy of the absorption edges present in the spectra of these sources. We present the latest results of the analysis of interstellar dust in dense environments of the Galaxy, using X-ray spectroscopy (Zeegers et al. 2016, submitted). Here we focus on the Si K-edge, where we make use of new synchrotron measurements of interstellar dust analogues. For the first time, we were able to characterize the Si extinction feature in great detail, giving a new insight on the chemical composition along the line sight and on the dust size distribution.

The temperature of interstellar dust Seyit Hocuk1 1MPE, Garching, Germany The interstellar dust temperature is a key parameter in astrochemical studies that governs the rate at which species form on dust. It also plays a crucial role in the thermodynamics of interstellar clouds, because of the gas-dust collisional coupling. I aim to shed light on the critical dependencies of the dust temperature by analytically solving it from first principles for different types of grain material and to correlate it with a collection of recent observational measurements. The dust temperature is obtained in two ways: semi-analytically by assuming a thermal equilibrium between dust and its environment, and numerically by using the Monte Carlo radiative transfer code Radmc-3d. I also investigate the effect of ices and explore the impact of coagulation on the dust temperature. The results show that a mixed carbonaceous-silicate type dust with a high carbon volume fraction of 0.48 matches the observations best. It is found that ice formation keeps the dust from cooling to very low temperatures at high optical depths and that coagulation has no significant impact on the dust temperature. I provide an easy-to-use parametric expression as a function of visual extinction from the best matching dust models, with the possibility to scale the function by the ambient interstellar radiation field. Invited Talk:

Constraints on Dust Properties from Interstellar Polarization Nikolai V. Voshchinnikov St. Petersburg University, St. Petersburg, Russia We model the wavelength dependence of interstellar linear polarization and fit it in the Serkowski curve with three parameters. They characterize the maximum degree of polarization Pmax, the wavelength corresponding to it λmax and the width of the curve describing by the coefficient K. We use aligned silicate and non-aligned carbonaceous spheroidal particles with different aspect ratios and interpret the relations K-λmax and Pmax/E(B-V)-λmax. The observed trend between K and λmax can be explained if we vary the minimum size of aligned grains and consider the size distributions evolving due to gas accretion and grain coagulation. The polarizing efficiency Pmax/E(B-V) goes down dramatically when the size of polarizing grains grows. The variations of the degree and direction of particle orientation influence this ratio only moderately. We also find that the aspect ratio of prolate grains does not affect significantly the polarizing efficiency. For oblate particles, the shape effect is stronger but in most cases the polarization curves produced are too narrow in comparison with the observed ones.

Modeling Dust Polarization from the UV to the Microwave Brandon Hensley1, B. T. Draine2 1JPL/Caltech, Pasadena, CA, USA 2Princeton University, Princeton, NJ, USA I will describe a new dust model based on carbonaceous and silicate materials that, through use of aspherical grains, self-consistently describes dust polarization in both extinction and emission while respecting observed interstellar abundances. In addition to reproducing the new constraints from Planck and existing constraints on dust emission, extinction, and polarization from the UV to the microwave, these models make key testable predictions for the levels of dust polarization at frequencies where it has not been observed. Dust evolution in polarized and unpolarized Planck data Lapo Fanciullo1, Vincent Guillet1, François Boulanger1 1Institut d’Astrophysique Spatiale (IAS), Orsay, France Dust is processed in the interstellar medium (ISM) and its properties depend on its history and environment (e.g. Fitzpatrick & Massa 2007, Fanciullo et al. 2015); however, most interstellar dust models are static. The Planck survey will play an important role in the coming generation of dust models, which will need to not only fit a new set of observables, but also use evolution to explain the observed variations in dust properties (Planck intermediate results XIX, XX, XXI, XXII). My work at IAS developed on several fronts connected with this enterprise, such as the comparison of dust models to Planck data and the multi-wavelength study of dust extinction and emission, both polarized and non. Using a combination of dust emission observed with Planck and dust extinction from the SDSS QSO survey it was possible to calculate the dust emission per unit extinction (Planck intermediate results XXIX), thus breaking the degeneracy between dust opacity and temperature in the emission spectrum of dust. Thus allowed to obtain the first estimate of dust optical properties variations in the diffuse ISM (Fanciullo et al. 2015). Comparison between dust models and the emission per unit extinction show that the THEMIS model (Jones et al. 2013) fares better than other modern models (Draine & Li 2007, Compiègne et al. 2011). Polarized dust extinction and emission also provide information on aligned dust grains in magnetic fields. We employ polarized, multi-wavelength data on both dust extinction and emission, and we compare them to the results of a polarized dust model derived from Compiègne (Guillet et al., in preparation) with variable dust alignment, magnetic field orientation and grain growth. I will show how variations in these parameters, both

singularly and in combination, can explain most of the observed data, and how the use of both extinction and emission helps break the degeneracy between these parameters (Fanciullo et al., in preparation). Invited Talk:

Evolving dust in the Milky Way and beyond Cesare Cecchi-Pestellini1, Giacomo Mulas2, Alberto Zonca2 1INAF – Osservatorio Astronomico di Palermo, Palermo, Italy 2INAF – Osservatorio Astronomico di Cagliari, Cagliari, Italy Dust grains are formed in several types of near-stellar environment. However, once they enter the interstellar medium these grains will be modified in size, shape and even composition by a variety of physical processes. These modifying processes may continue to act throughout the lifetime of a grain. Thus, we should really consider the possibility that grains evolve in the interstellar medium. In the diffuse medium, some materials will be affected by starlight or by cosmic rays, and some may be modified by chemical reactions with gas phase species. All grains will be eroded and possibly reduced to atoms or small molecular fragments in the intermittent passage of interstellar shock waves, with some materials (such as silicates) being more resistant to this kind of erosion than others (such as hydrocarbon polymers). The response of dust to local conditions may be reflected in the variations in interstellar extinction curves along different lines of sight in the Milky Way, and in other galaxies. We present here a dust model specifically constructed on the assumption that dust grains evolve in space. From considerations of the relative responses to shocks of silicate and carbon materials we consider a population of grains in which a multi-layered carbon mantle is deposited on a silicate core. This is supplemented by a suite of 54 PAHs in 4 charge states. The model is inherently time-dependent with its properties modified by the interaction with the environments in which grains are embedded. Timescales are set by the deposition time of carbon in a hydrogen-rich gas (mainly aliphatic), and the time for its conversion to aromatic carbon by the local ultraviolet radiation field. Another timescale is associated with the occasional swift ablation of the carbon layers and their recycling in the gas-phase (possibly in the form of PAHs) when a shock occurs.

The Optical-Infrared Extinction Curve and its Variation in the Milky Way Eddie Schlafly1 1LBNL, Berkeley, USA The dust extinction curve is a critical component of many observational programs and an important diagnostic of the physics of the interstellar medium. Here we present new measurements of the dust extinction curve and its variation toward tens of thousands of stars, a hundred-fold larger sample than in existing detailed studies. We use data from the APOGEE spectroscopic survey in combination with ten-band photometry from Pan-STARRS1, the Two Micron All-Sky Survey, and Wide-field Infrared Survey Explorer. We find that the extinction curve in the optical through infrared is well characterized by a one-parameter family of curves described by R(V). The extinction curve is more uniform than suggested in past works, with sigma(R(V)) = 0.18, and with less than one percent of sight lines having R(V) > 4. Our data and analysis have revealed two new aspects of Galactic extinction: first, we find significant, wide-area variations in R(V) throughout the Galactic plane. These variations are on scales much larger than individual molecular clouds, indicating that R(V) variations must trace much more than just grain growth in dense molecular environments. Indeed, we find no correlation between R(V) and dust column density up to E(B-V) ~ 2. Second, we discover a strong relationship between R(V) and the far-infrared dust emissivity. Invited Talk: Grain Size Distribution in the Dense ISM Jürgen Steinacker1,2,3, Thomas Henning3, Aurore Bacmann1,2 1Univ. Grenoble Alpes, IPAG, F-38000 Grenoble, France 2CNRS, IPAG, F-38000 Grenoble, France 3Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany The change from the diffuse interstellar medium to its denser parts goes along with a change of relevant physical processes that impact the chemical composition of the gas as well as the dust properties. We review the observations of the dense ISM that are modeled to interpret the grain size distribution and the chemical properties of the grains. In the framework of turbulence-driven coagulation, we review the existing models and their implication for the size distribution. Finally, we will discuss recent findings on the high-mass tail of the size distribution probed by mid-infrared coreshine, and alternative interpretations based on specific coating of the grains. We will close with an outlook discussing indications for the complete absence of grain growth in the densest parts of the ISM.

3. Formation and destruction processes Invited Talk: Dust formation in evolved stars and supernovae Isabelle Cherchneff1 1Departement Physik, Universität Basel, Switzerland Sources of cosmic dust in the local and far universe include evolved low- and high- mass stars and core-collapse supernovae. These stellar environments, specifically the winds of stars and the material ejected by supernova, are characterised by high gas densities and temperatures, and long residency time. These conditions are required to efficiently form molecular clusters, which grow to dust grains through accretion, coalescence and coagulation. Spitzer, Herschel and ALMA have provided new insights on the type and quantity of dust produced by evolved stars and supernovae. New theoretical models further our understanding of the processes that underpin dust synthesis. However, many unsolved issues remain and are related to the chemical nature of the condensates, the mechanisms triggering dust formation, the evolution of dust grains at late time, e.g. dust survival in supernova remnants, and the relative contributions of these evolved environments to the dust budget of galaxies. I will discuss the current challenges related to the formation of cosmic dust in stellar sources and supernovae. Dust evolution between diffuse ISM Phases in the light of Planck François Boulanger1, Lapo Fanciullo1, Tuhin Ghosh2, Urmas Haud3, Anthony Jones1, Peter Kalberla4 , Vincent Guillet1, Marc-Antoine Miville-Deschênes1 and Nathalie Ysard1 1Institut d’Astrophysique Spatiale, Orsay, France 2California Institute of Technology, Pasadena, CA, USA 3Tartu Observatory, Tõravere, Estonia 4Argelander-Institut fur Astronomie , Bonn, Germany

The composition of interstellar dust is thought to reflect the action of interstellar processes, which contribute to break and re-build grains over time scales much shorter than the injection of newly condensed stardust. In particular, refractory mantles formed on grains by accretion of gas species must account for a substantial fraction of the interstellar dust mass in the cold interstellar medium. The observed variations in depletions are direct evidence that the cycling of refractory elements off and on dust grains is effective within the diffuse interstellar medium. However no observational

signature of the formation and destruction of grain mantles have yet been identified in dust emission data. I will report results from the Planck space mission that change this perspective. The analysis and the modelling of Planck observations have revealed variations, within the diffuse interstellar medium, of the far-IR/sub-mm dust spectral energy distribution (SED), normalized per hydrogen or the E(B-V) reddening, analogous to those observed with earlier observations in molecular clouds. Using a Gaussian decomposition of HI 21cm spectra from the Parkes Galactic All Sky Survey, we show that the observed variations reflect a systematic change in the dust SED from the warm to the cold neutral cold medium (WNM and CNM). We find that the CNM dust is colder than the WNM dust and that it has substantially higher sub-mm opacity per hydrogen. We interpret this result as a signature of the formation of refractory mantles by accretion in CNM. Within this interpretation accretion is observed to occur within parsecs-scale CNM structures formed out of the WNM by thermal instability, prior to the formation of H2. I will discuss these new results in the general context of current modelling of the composition of interstellar dust and its life cycle. Modelling dust evolution in galaxies with a multiphase, inhomogeneous ISM Svitlana Zhukovska1, Clare Dobbs2, Edward B. Jenkins3, Ralf Klessen4 1Max Planck Institute for Astrophysics, Garching, Germany 2University of Exeter, Exeter, United Kingdom 3Princeton University Observatory, Princeton, NJ 08544-1001, USA

4Zentrum für Astronomie der Universität Heidelberg, Institut für Theoretische Astrophysik, Albert-Ueberle-Str. 2, D-69120 Heidelberg, Germany I will present a new model of dust evolution in a multiphase, inhomogeneous ISM using hydrodynamical simulations of giant molecular clouds in a Milky Way-like spiral galaxy. The model includes an improved treatment of dust growth by accretion in the ISM to investigate the role of the temperature-dependent sticking coefficient and ion-grain interactions. The local Galaxy offers unprecedented observational data on Si gas abundances [Si/H]gas along numerous lines of sight which probe a wide range of physical conditions. Using these data, we derive a relation between the average [Si/H]gas and the local gas density n that we use as a critical constraint for the models. This relation requires an efficiency of sticking of gas species impinging grain surface to decrease with gas temperature. I will demonstrate that the dust growth by accretion provides a natural explanation to the observed relation between [Si/H]gas and local gas density. The shape of the synthetic relation is however sensitive to the grain size distribution and enhancement of collision rates due to Coulomb interactions.

Finally, I will discuss relative contributions from stars and growth in the ISM to the dust budget of the local Milky Way and the timescales of these processes. Invited Talk: The Micro- and Macrophysics of Grain Destruction Eli Dwek1, Jonathan D. Slavin2, and Anthony, P. Jones3 1NASA Goddard Space Flight Center, Greenbelt, MD, USA 2Smithsonian Astrophysical Observatory, Cambridge, MA, USA 3Institute d’Astrophysique Spatial (IAS), Orsay, France Dust is generated in the quiescent ejecta of AGB stars and in the explosively ejected debris of core collapse supernovae (CCSNe). The maximum mass of dust in galaxies is limited by the mass of available refractory elements in the interstellar medium (ISM). It is further limited by its finite lifetime in the ISM. Determining the lifetime of dust requires detailed knowledge of the micro- and macroscopic processes leading to its destruction. Microscopically, it requires knowledge of the dust composition, the physical properties of the dust, the sputtering efficiencies, and the outcomes of grain-grain collisions. Macroscopically, it depends on the frequency and energy of supernova explosions, and the density, morphology, and magnetic field strength of the ISM. In this talk I will review the major processes that determine the dust lifetime, and their uncertainties.

Dust emission associated with ionized gas Russell Shipman1

1 SRON: Netherlands Institute for Space Research

Within the Rosette Nebula, at the northern edge of the central cavity is a strong ridge of 22 micron mid-infrared emission. This dust component appears to be well mixed with the ionized gas. The nature of this emission is explored using standard dust grain models. Even in the strong UV radiation field of the Rosette Nebula, the classical large dust grains cannot achieve high enough temperatures to be the source of the emission. PAH emission features are shown to be present only at the edge of the ionisation front, not within the ionized region. We explore the possibility that this excess emission is due to a robust dust component made up of very small, non-equilibrium dust particles which can survive the hard UV radiation field within the Rosette Nebula.

The turbulent life of dust grains in the supernova-driven, multi-phase interstellar medium Thomas Peters, Svitlana Zhukovska, Thorsten Naab Max Planck Institute for Astrophysics, Garching, Germany Dust grains are an important component of the interstellar medium (ISM) of galaxies. In my talk, I will present the first direct measurement of the residence times of interstellar dust in the different ISM phases, and of the transition rates between these phases, in realistic hydrodynamical simulations of the multi-phase ISM. The simulations include a time-dependent chemical network that follows the abundances of H^+, H, H_2, C^+ and CO and take into account self-shielding by gas and dust using a tree-based radiation transfer method. Supernova explosions are injected either at random locations, at density peaks, or as a mixture of the two. For each simulation, we investigate how matter circulates between the ISM phases and find more sizeable transitions than considered in simple mass exchange schemes in the literature. The derived residence times in the ISM phases are characterised by broad distributions, in particular for the warm and hot medium. The most realistic simulations with random and mixed driving have median residence times in the molecular, cold, warm and hot phase around 17, 7, 44 and 1 Myr, respectively. The transition rates measured in the random driving run are in good agreement with observations of Ti gas-phase depletion in the warm and cold phases predicted by a simple depletion model, although the depletion in the molecular phase is under-predicted. ISM phase definitions based on chemical abundance rather than temperature cuts are physically more meaningful, but lead to significantly different transition rates and residence times because there is no direct correspondence between the two definitions.

4. Dust coagulation models

Dust in Dense Molecular Clouds and Protoplanetary Disks Alexei Ivlev1, Vitaly Akimkin2, Marco Padovani3,4, Daniele Galli4, Paola Caselli1 1Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany 2Institute of Astronomy of the Russian Academy of Sciences, Moscow, Russia 3Université de Montpellier, Montpellier, France 4Osservatorio Astrofisico di Arcetri, Firenze, Italy Ionization-recombination balance in dense interstellar and circumstellar environments is a key component for a variety of physical processes, such as chemical reactions, dust

charging and coagulation, coupling of the gas with magnetic field and the development of magnetorotational instability in protoplanetary disks. Dust plays exceptionally important role in these processes, and its evolution provides crucial feedback to the ionization equilibrium. We present a self-consistent analytical approach to exactly calculate abundances of charged species in dense dusty gas, in the regime where the recombination on dust dominates over the gas-phase recombination. In particular, we obtain the dust charges for arbitrary grain size distributions, point out the critical role played by small dust, and discuss hitherto completely neglected mechanism of dust charging in such environments by cosmic rays. Coagulation of Charged Dust in Protoplanetary Disks Vitaly Akimkin Institute of astronomy of the Russian academy of sciences, Moscow, Russia

Electrostatic interaction affects collisional cross-section of charged dust grains. Photoelectric and collisional charging are two primary mechanisms driving grains to positive and negative potentials, respectively. By solving the Smoluchowski equation for protoplanetary disk conditions, we show, that effective coagulation occurs in a layer at intermediate heights, where these two charging mechanisms compete and both negative and positive grains are present. In dark regions, where the collisional charging dominates and grains are mostly negatively charged, the electrostatic barrier effectively hampers grain growth. Similarly, in an illuminated disk atmosphere, the photoelectric charging retains positively charged population of small grains. We speculate, that enhanced coagulation near zero-charge surface could also operate in outer regions of dense cores.

Invited Talk: From Dust to Planetesimals Til Birnstiel

Max-Planck-Institute for Astronomy, Heidelberg, Königstuhl 17, 69117 Heidelberg

Solids in circumstellar disks are inherited from the interstellar medium: dust particles at most a micrometer in size. Protoplanetary disks are the environments where these particles need to grow at least 13 orders of magnitude in size. Our understanding of this growth process is far from complete, with different physics seemingly posing obstacles at various stages of the process. Still, the ubiquity of planets in our galaxy suggests that planet formation is a robust mechanism.

This talk focuses on the early stages of planet formation, the growth of small dust grains towards the gravitationally bound "planetesimals", the building blocks of planets. I will introduce the key physics involved in the growth processes and discuss how they are expected to shape the global behavior of the solid content of disks. I will consider possible pathways towards the formation of larger bodies and conclude by reviewing some of the recent observational advances in the field that foreshadow an exciting future of the field of planet formation and its chemistry. 5. Experimental studies Invited Talk: Cold Synthesis of Carbon and Silicate Dust Gaël Rouillé1, 2, Cornelia Jäger1, 2, Thomas Henning1 1Max Planck Institute for Astronomy, Heidelberg, Germany 2Friedrich Schiller University Jena, Jena, Germany Diverse observations support the notion that cosmic dust grains grow in the interstellar medium (ISM). Primary refractory particles are formed in stellar envelopes at relatively high temperatures and a fraction of them are transferred into the ISM. At the low temperatures that prevail in the ISM, the primary particles that have survived the onslaught of cosmic rays and shock waves would grow through accretion of atoms and molecules from the gas phase. Further, the nanometer-sized particles would coagulate into micrometer-sized aggregates. In the ISM, the cold surface of dust grains can adsorb various atomic and molecular species. Ice layers, volatile, can be formed. Incident VUV photons deliver energy that may enable desorption or chemical reactions. Some chemical reactions, however, do not require an input of external energy and may be the key to the growth of refractory cores at very low temperatures. Our group carries out experiments to study the condensation of refractory materials by accretion of cold atoms and molecules at cryogenic temperatures. These refractory materials are those constituting most of the cosmic dust, i.e., complex silicates and solid carbon. We will describe our experiments and review their results, which will be discussed in the astrophysical context. Invited Talk: Interaction of Cosmic Rays & UV with ISM carbonaceous analogues: some laboratory experimental simulations

Emmanuel Dartois1, Ivan Alata2, Markus Bender3, Karine Beroff2, Marin Chabot4, Gustavo A. Cruz-Diaz5,6, Marie Godard7, Aurélie Jallat4, Rafael Martín-Doménech5, Guillermo M. Muñoz Caro5, Thomas Pino2, Daniel Severin3, Christina Trautmann3 1Institut d'Astrophysique Spatiale, CNRS, Univ. Paris Sud & Paris-Saclay, 91405 Orsay, France 2Institut des Sciences Moléculaires d'Orsay, CNRS, Univ. Paris Sud & Paris-Saclay, 91405 Orsay, France 3GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt, Germany 4Institut de Physique Nucléaire d'Orsay, IN2P3-CNRS, Univ. Paris Sud & Paris-Saclay, 91405 Orsay, France 5Centro de Astrobiología, INTA-CSIC, Carretera de Ajalvir, km 4, Torrejón de Ardoz, 28850 Madrid, Spain 6NASA Ames Research Center, Moffett Field, Mountain View, CA 94035, USA 7Centre de Sciences Nucléaires et de Sciences de la Matière, CNRS/IN2P3, Univ. Paris Sud & Paris-Saclay, 91405 Orsay, France

The interstellar dust grains are immersed in a permanent flux of cosmic rays and ultraviolet photons. The penetration of cosmic rays in the dense molecular clouds regions, protected from the standard interstellar UV photons, produces new species via radiolysis of these solids and cosmic ray induced secondary UV photons. The cosmic rays also affect the structure of solids and induces desorption of species in the gas phase by electronic sputtering. In diffuse environments and interfaces of molecular clouds, the more refractory carbonaceous and mineral dust grains are also modified under the effect of cosmic rays. The interstellar high-energy cosmic rays can be simulated in the laboratory for a better understanding of astrophysical processes. The high-energy cosmic ray component (just below or above 100 MeV/u) was so far only scarcely simulated experimentally. Nevertheless, there is a clear need to study the interaction of high energy cosmic rays with interstellar analogues, since the energy deposited on dust grains is expected to be important compared to protons, and concomitant with UV photons. This talk will be dedicated to describe the evolution, in an astrophysical context and based on laboratory experiments, of hydrogenated amorphous carbon dust analogues, including sputtering, resulting from the interactions with swift ions and UV photons.

Growth and Destruction of PAH Molecules in Reactions with C Atoms Serge Krasnokutski, Friedrich Huisken, Cornelia Jäger, Thomas Henning Laboratory Astrophysics Group of the Max Planck Institute for Astronomy at the Friedrich Schiller University Jena, Institute of Solid State Physics, Helmholtzweg 3, D-07743 Jena, Germany

Polycyclic aromatic hydrocarbon (PAH) molecules are believed to be abundant in the interstellar medium (ISM).1 They can be a part of larger carbonaceous grains as well as be present separately in the gas-phase creating a population of ultra-small grains. The large portion of carbon in the ISM exists in the form of the atomic gas.2 Therefore, the condensation of the carbon atoms and their reaction with PAHs could be an important mechanism for the growth of the carbonaceous interstellar grains. We performed a set of laboratory and computational studies of the reactions of carbon atoms in the ground state with naphthalene, anthracene, and coronene molecules. The reactions has been investigated in liquid helium droplets at T = 0.37 K and by quantum chemical computations. Our studies suggest that all small PAHs and large catacondensed ones react barrierlessly with atomic carbon, and therefore their abundancies should be efficiently depleted by such reactions in a broad temperature range. The reaction also leads to the increase of molecular size of PAHs. At the same time, large compact pericondensed PAHs should be more inert toward such a reaction. Taking into account the higher photostability of pericondensed PAHs, their much higher abundances should be expected in different astrophysical environments. The results suggest that condensation of atomic carbon at low-temperatures may lead to the growth of PAH molecules till specific sizes. After reaching these sizes the growth of PAHs should be slowed down and the formation of aliphatic bonds dominates. 1. Tielens, A. G. G. M., Interstellar Polycyclic Aromatic Hydrocarbon Molecules*. Annu. Rev. Astron. Astr. 2008, 46 (1), 289-337. 2. Snow, T. P.; Witt, A. N., The Interstellar Carbon Budget and the Role of Carbon in Dust and Large Molecules. Science 1995, 270 (5241), 1455-1460. Far infrared spectroscopy of dust analogs at low temperatures Pierre Mohr1, Harald Mutschke1, Frank Lewen2, Tim Dressler2 1Astrophysik.Inst., Friedrich-Schiller-Univ. Jena, Jena, Germany 2l. Physik. Inst, Universität zu Köln, Cologne, Germany We have measured far infrared and (sub-)mm opacities of amorphous silicates, which are a main constituent of interstellar dust and are also found in other environments such as protoplanetary disks and debris disks. As analog materials for amorphous dust, we produced glasses of pyroxene- and olivine-like composition with various Mg/Fe-ratio by rapid quenching of siliceous melts. For our measurements, we applied a LHe cryostat which can be placed directly in the beamline of the spectrometer, allowing us to take transmission spectra between room temperature and 10 K. Besides the known temperature dependence of the absorption in the far infrared region we also found a strong dependence on the iron content of our samples and the oxidation state of iron (determined by Mössbauer spectroscopy). In order to change the ratio of divalent to trivalent iron in our samples we annealed them below their glass transition temperature in a gas-mixing furnace with adjustable oxygen fugacity.

6. Extragalactic dust Simulating the dust content of galaxies: successes and failures Ryan McKinnon1, Paul Torrey1,2, Mark Vogelsberger1, Christopher C. Hayward2,3, Federico Marinacci1 1Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA

2TAPIR, California Institute of Technology, Pasadena, CA 91125, USA

3Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 USA

We present full volume cosmological simulations using the moving-mesh code AREPO to study the coevolution of dust and galaxies. We extend the dust model in AREPO to include thermal sputtering of grains and investigate the evolution of the dust mass function, the cosmic distribution of dust beyond the interstellar medium, and the dependence of dust-to-stellar mass ratio on galactic properties. The simulated dust mass function is well-described by a Schechter fit and lies closest to observations at z = 0. The radial scaling of projected dust surface density out to distances of 10 Mpc around galaxies with magnitudes 17 < i < 21 is similar to that seen in Sloan Digital Sky Survey data. At z = 0, the predicted dust density of Ωdust ≈ 1.9 × 10-6 lies in the range of Ωdust values seen in low-redshift observations. We find that dust-to-stellar mass ratio anti-correlates with stellar mass for galaxies living along the star formation main sequence. Moreover, we estimate the 850 µm and 1.1 mm number density functions for simulated galaxies at z = 1 and analyse the relation between dust-to-stellar flux and mass ratios at z = 0. At high redshift, our model fails to produce enough dust-rich galaxies, and this tension is not alleviated by adopting a top-heavy initial mass function. We do not capture a decline in Ωdust from z = 2 to z = 0, which suggests that dust production mechanisms more strongly dependent on star formation may help to produce the observed number of dusty galaxies near the peak of cosmic star formation.

The evolution of the dust content of galaxies in cosmological simulations of galaxy formation Gergö Popping1

1 ESO, Karl-Schwarzschild-Strasse 2 85748, Garching, Germany

Dust is a key ingredient of the interstellar medium and in galaxy physics. Nevertheless, dust chemistry is typically not included in cosmological models of galaxy formation. I will

introduce a new semi-analytic model of galaxy formation that includes a dust chemistry model. The model tracks the condensation of dust in stellar ejecta, the growth of dust in the dense ISM, the destruction of dust by thermal sputtering, dusty winds from star-forming regions, and the infall of dust from the CGM. I will show how different approaches to model the accretion of dust in the ISM affect the dust content of galaxies. I will then discuss the evolution in the dust content, the dust-to-gas, and dust-to-metal ratio for galaxies covering a wide range in stellar masses, star-formation rates, and metallicities, from redshift seven to zero. I will also show the relative importance of different dust formation/growth channels over cosmic time and for different classes of galaxies. I will finish by demonstrating the relevance of metal depletion onto dust grains and how accounting for this reveals a caveat in our understanding of the metal buildup of galaxies.

Far-infrared and dust properties of present-day galaxies in the EAGLE simulations Peter Camps1, James W. Trayford2, Maarten Baes1, Tom Theuns2, Matthieu Schaller2, Joop Schaye3 1Sterrenkundig Observatorium, Universiteit Gent, Belgium 2Institute for Computational Cosmology, University of Durham, UK 3Leiden Observatory, Leiden University, the Netherlands The EAGLE cosmological simulations reproduce the observed galaxy stellar mass function and many galaxy properties. In this work, we study the dust-related properties of present-day EAGLE galaxies through mock observations in the far-infrared and submm wavelength ranges obtained with the 3D dust radiative transfer code SKIRT. To prepare an EAGLE galaxy for radiative transfer processing, we derive a diffuse dust distribution from the gas particles and we re-sample the star-forming gas particles and the youngest star particles into star-forming regions that are assigned dedicated emission templates. We select a set of redshift-zero EAGLE galaxies that matches the K-band luminosity distribution of the galaxies in the Herschel Reference Survey (HRS), a volume-limited sample of about 300 normal galaxies in the Local Universe. We find overall agreement of the EAGLE dust scaling relations with those observed in the HRS, such as the dust-to-stellar mass ratio versus stellar mass and versus NUV-r colour relations. A discrepancy in the f_250/f_350 versus f_350/f_500 submm colour-colour relation implies that part of the simulated dust is insufficiently heated, likely because of limitations in our sub-grid model for star-forming regions. We also investigate the effect of adjusting the metal-to-dust ratio and the covering factor of the photodissociation regions surrounding the star-forming cores. We are able to constrain the important dust-related parameters in our method, informing the calculation of dust attenuation for EAGLE galaxies in the UV and optical domain.

Properties of Interstellar Dust as Probed by Extinction Laws toward Type Ia Supernovae Takaya Nozawa1 1National Astronomical Observatory of Japan, Tokyo, Japan Despite the great advance in understanding of properties of dust in the Milky Way (MW), our knowledge of interstellar dust in external galaxies remains scarce. This may be because measurements of extinction curves, which offer key clues on composition and size distribution of interstellar dust, are challenging works for galaxies beyond the MW. In this talk, I first demonstrate that Type Ia supernovae (SNe Ia) are ideal targets from which we can derive the interstellar extinction laws in external galaxies. In particular, SNe Ia appear in every type of galaxies so that the extinction laws along lines of sight to SNe Ia can probe the properties of interstellar dust in a variety of galaxies. However, most of the observations so far have suggested that the extinction curves toward SNe Ia are highly steep with unusually low total-to-selective extinction ratios less than Rv = 2.0. Then, in order to reveal the properties of interstellar dust that causes such unusual extinction laws, we search for physical dust models that lead to good fits to the extinction curves with Rv = 2.0, 1.5, and 1.0. We find that the steep extinction curves with Rv = 2.0, 1.5, and 1.0 can be reasonably explained even by the simple power-law dust models with an index of -3.5 by taking the maximum cut-off radii of 0.13 um, 0.094 um, and 0.057 um, respectively. These maximum cut-off radii are smaller than ~0.25 um considered valid in the MW, clearly demonstrating that the interstellar dust responsible for steep extinction curves is biased to smaller sizes. Finally I will discuss the possible reasons why interstellar dust in external galaxies is small compared with that in the MW. Dust in Andromeda, linking models to observations Sébastien Viaene Universiteit Gent, Belgium The Andromeda galaxy (M31) is the closest large galaxy to our own Milky Way. Its proximity makes it an ideal laboratory to investigate both local and global galaxy properties. Within the Herschel Exploitation of Local Galaxy Andromeda (HELGA) project, we have studied M31 in detail from UV to sub-mm, with particular emphasis on the dust physics. We performed pixel-by-pixel SED modelling and constructed dust scaling relations which reveal the delicate balance between dust destruction and production. Furthermore, the dust heating mechanisms in the galaxy are studied by creating a panchromatic 3D radiative transfer model. This model incorporates realistic distributions for several stellar populations and for interstellar dust. We compare our model to observations, and test several tracers for dust heating sources. I will discuss our results in the context of dust evolution and starlight reprocessing.

Invited Talk: Dust and gas shaping the evolution of high-redshift galaxies Dieter Lutz1 1Max-Planck-Institut für extraterrestrische Physik, Garching, Germany In the current ‘equilibrium’ picture of galaxy evolution, constant influx of fresh gas from the cosmic web or minor mergers sustains the substantial star formation rates of normal star forming ‘main sequence’ galaxies. In the interplay of inflow, star formation, metal enrichment, and outflow, measuring the ISM content is crucial, and dust-based methods have gained importance rivalling the traditional tracing of molecular gas by CO. I will summarize recent determinations of ISM content and scaling relations for z<~2.5 galaxies based on dust and CO as measured with Herschel, ALMA, and IRAM-NOEMA, and the challenges of extending these studies both to yet higher redshifts and to lower mass galaxies. Connecting Interstellar Dust and Gas Properties in Galaxies using Quasar Absorption Systems at z≤1 Monique C. Aller1, Varsha P. Kulkarni2, Eli Dwek3, Donald G. York4, Daniel E. Welty4, Giovanni Vladilo5 1Department of Physics, Georgia Southern University, Statesboro, GA, USA 2Department of Physics and Astronomy, University of South Carolina, Columbia, SC, USA 3NASA Goddard Space Flight Center, Greenbelt, MD, USA 4Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL, USA 5Osservatorio Astronomico di Trieste, Trieste, Italy Quasar absorption systems (QASs) provide an optimal tool to study both the interstellar dust and gas in normal galaxies that lie along the sightlines to luminous background quasars. Using spectroscopy of the background quasars, we have established the presence of silicate dust grains in gas- and metal-rich QASs. We find that in these systems the silicate dust exists at 3-6 times higher optical depths than we would expect for comparable diffuse gas in the Milky Way, suggesting differences in the silicate dust grains. We also find differences in the shape of the silicate feature absorption line profiles between individual systems, suggestive of variations in the dust grain crystallinity and composition. We present results from our program studying the silicate dust and gas properties in z≤1 QASs with multi-wavelength archival data, using Spitzer IRS low-resolution spectra to measure the 10 and 18 micron silicate dust absorption

features, and using rest-frame UV/optical spectra to study the metal lines arising in the gas phase. We investigate variations in silicate dust grain properties between galaxies, as well as correlations between the silicate dust abundance, reddening, and gas metallicity. We also examine the relationship between the silicate dust and carbonaceous dust, for those QASs that have 2175 Å data. These measurements will ultimately yield valuable insights into dust production mechanisms, and into the chemical enrichment and star formation histories of these galaxies. This work is being supported by NASA through ADAP grant NNX14AG74G. Dust depletion in damped Lyman-alpha absorbers: a unified picture from low-metallicity systems to the Galaxy Annalisa De Cia1, C. Ledoux2, L. Mattsson3, P. Petitjean4, R. Srianand5, I. Gavignaud6, E.B. Jenkins7 1European Southern Observatory, Garching bei München, Germany 2European Southern Observatory, Santiago, Chile 3Nordita, Stockholm, Sweden 4IAP, CNRS, Paris, France 5IUCAA, Pune, India 6Universidad Andres Bello, Santiago, Chile 7Princeton University Observatory, Princeton, USA We study metal relative abundances in a sample of 70 damped Lyman-alpha absorbers (DLAs) with 2 < z < 4, all observed at high spectral resolution with VLT/UVES, and including measurements for Galactic clouds. We observe tight correlations among relative abundances, due to dust depletion, and derive dust-depletion sequences that are continuous from DLAs to the Galaxy. We separate and characterize the effects of dust depletion, nucleosynthesis, and metallicity. We further derive dust properties, such as the dust-to-metal ratio, dust extinction and the elemental abundances in dust, which is an important step to understanding the dust composition in these systems.

The evolution of the dust-to-metals ratio in high-redshift galaxies probed by GRB-DLAs Philip Wiseman1 1Max-Planck-Institute für Extraterrestrische Physik (MPE), Giessenbachstrasse 1, 85748 Garching, Germany

Several issues regarding the nature of dust at high redshift remain unresolved: its composition, its production and growth mechanisms, and its effect on background sources. We aim to provide a more accurate relation between dust depletion levels and dust-to-metals ratio (DTM), and to use the DTM to investigate the origin and evolution of

dust in the high redshift Universe via GRB-DLAs. We use absorption-line measured metal column densities for a total of 19 GRB-DLAs, including five new GRB afterglow spectra from VLT/X-shooter. We use the latest linear models to calculate the dust depletion strength factor in each DLA. Using this we calculate total dust and metal column densities to determine a DTM. We explore the evolution of DTM with metallicity, and compare this to previous trends in DTM measured with different methods. We find significant dust depletion in 16 of our 19 GRB-DLAs, yet 18 of the 19 have a DTM significantly lower than the Milky Way. We find that DTM is positively correlated with metallicity, which supports a dominant ISM-grain-growth mode of dust formation. We find a substantial discrepancy between the dust content measured from depletion and that derived from the total V-band extinction, AV, measured by fitting the afterglow SED. We advise against using a measurement from one method to estimate that from the other, until the discrepancy can be resolved.

The formation and evolution of high-redshift dust

Raffaella Schneider1

1INAF/Osservatorio Astronomico di Roma

The presence of dust at z > 6 requires efficient formation in supernova ejecta and in the winds of the most massive AGB stars. In quasar host galaxies, efficient grain growth in the metal-enriched interstellar medium is required to explain the large far infrared luminosities observed. At the same time, ALMA is providing the first probes of the dust content of normal star forming galaxies.

In this talk, I will review recent work on the modelling of dust formation and evolution at high redshift, making direct comparison to observational data.

Abstracts of Poster contributions

The variation of the dust attenuation curve in the nearby Universe Marjorie Decleir1, Ilse De Looze2, Maarten Baes1 1University of Ghent, Belgium 2University College of London, United Kingdom A full understanding of the dust properties in galaxies and the interplay between dust and starlight is essential to recover the starlight obscured by dust, and to determine the energy balance between gas heating and cooling processes. It is hence fundamental to probe the current and past star formation activity and to constrain the cosmic star formation history. In extragalactic studies, the dust attenuation law is usually assumed to be similar to the Milky Way for normal galaxies, while the so-called Calzetti relation is used for starburst galaxies. However, there is growing evidence for strong deviations from a universal dust attenuation law. We have initiated an ambitious program to study the variation of the dust attenuation curve and the dust properties in the nearby Universe. It is based on the SINGS/KINGFISH sample, a unique local galaxy sample spanning a wide range of morphological galaxy types, metal abundances and star formation activity. We are gathering multi-wavelength imaging data for this sample, covering the UV to the submillimeter wavelength range. By fitting theoretical models with varying dust extinction properties to these data, it is possible to constrain the spectral energy distributions and the dust attenuation curves of nearby galaxies. Particularly important for our goal are UV data from the SWIFT telescope: the three UVOT filters uniquely cover the dust absorption feature at 2175 Å, which enables us to characterize the slope and bump strength in the attenuation curves of galaxies. We present the first results of our analysis of the variation of the dust attenuation curve on spatially resolved scales of about 200 pc in the spiral galaxy NGC 628. From these results it will be possible to determine whether the extinction properties of this galaxy resemble those of the Milky Way or more those of the Small or Large Magellanic Clouds or maybe neither of these... Cometary dust particles collected in the inner coma of comet 67P/Churyumov-Gerasimenko by COSIMA onboard Rosetta Martin Hilchenbach et COSIMA Team Max Planck Institute for Solar System Research, Göttingen, Germany

COSIMA, the COmetary Secondary Ion Mass Analyzer, is one of the three in-situ dust instruments onboard the Rosetta spacecraft, the ESA mission to comet 67P/Churyumov-Gerasimenko. Since August 2014, Rosetta has been escorting the comet nucleus on its journey inwards and outwards the inner solar system. The instrument COSIMA is collecting cometary dust particles by exposing metal targets in the inner coma, from 10 to hundreds of kilometers off the cometary nucleus. The targets are imaged with an optical microscope and a selection of the collected particles are analyzed by secondary ion mass spectrometry (SIMS). Thousands of dust particles have been collected and the sizes of the particles range up to sub-millimeter sizes and their differential size distribution has a mean power law exponent of about -3. The mass spectra contain either positive or negative ions revealing both, mineral and organic, components of the grains originating from selected surface area. Particle morphologies appear to be similar to that of interplanetary dust particles (IDPs). The particle mineral composition is consistent with the presence of minerals such as olivine and pyroxene and the overall elemental composition with CI chondrites, the organic matter in the refractory phases is similar to the insoluble organic matter in carboneous meteorites. Laboratory measurements of the far-infrared to millimeter opacity of carbonaceous dust-analogues Greif Jonas1, Mutschke Harald1 1Astrophysical Institute and University Observatory, University Jena, Germany We are measuring and analysing the FIR- and THz - Spectra of pyrolized micro-crystalline cellulose as an analogue of carbonaceous interstellar dust. We are using cellulose-powder with crystal sizes of 50 and 20 microns and are heating it up to 1000°C. Furthermore, we are going to calculate the emission cross section of particles with different geometry to compare them with the measured results. Dust in the wind: the mineralogy of newly formed dust in Active Galactic Nuclei Kemper Ciska1, Srinivasan Sundar1, Hao Lei2, Scicluna Peter1, Xie Yanxia3, Gallagher Sarah4, Ho Luis3 1Academia Sinica, Institute of Astronomy and Astrophysics, Taipei, Taiwan

2Shanghai Astronomical Observatory, China

3Kavli Institute for Astronomy and Astrophysics, Peking University, China

4Department of Physics and Astronomy, University of Western Ontario, Canada

The detection of large amounts of dust (Priddey et al. 2003; Beelen et al. 2006) in the early universe still remains largely unexplained. The traditional (stellar) dust sources do

not produce enough dust during the first Gyr to explain the reservoir of dust observed (Morgan & Edmunds 2003; Rowlands et al. 2014), and, furthermore, the extinction curves at high redshift are markedly different from those observed in the local universe (Maiolino et al. 2004; Stratta et al. 2007). Therefore, additional dust sources have been invoked, such as interstellar grain formation and grain growth (Martini et al. 2013). Additionally, by comparison with the dust forming environments around evolved low mass stars, Elvis et al. (2002) argue that the conditions in the wind coming off Active Galactic Nuclei (AGN) accretion disks allow for the formation of significant amounts of dust. This dust source would not only help explain the so-called dust budget crisis at high redshift, but also provides a natural explanation for the origin of the dusty AGN torus (Elitzur & Shlosman 2006).

We have started a project to determine the dust mineralogy towards a number of quasars where the dust features are seen in emission. We follow our earlier analysis of broad absorption line (BAL) quasar PG 2112+059 for which we have determined the mineralogical composition of dust using mid-infrared spectroscopy obtained with the Spitzer Space Telescope (Markwick-Kemper et al. 2007). From spectral fitting of the solid state features seen towards this object, we identify Mg-rich amorphous and crystalline silicates with olivine stoichiometry, as well as the more primitive condensates alumina (Al2O3) and periclase (MgO), probing the conditions in the dust condensation zone.

We have selected a sample of Palomar Green (PG) quasars with Herschel and AKARI photometry from the sample of Petric et al. (2015), and required their archival Spitzer spectra to show the 9.7 micron silicate feature in emission. The Herschel photometry will constrain the far-infrared continuum. We will chart the variety in mineralogy present in quasar winds, and compare the results with other work present in the literature (e.g. Köhler & Li 2010; Smith et al. 2010; Xie et al. 2014), studies which all have targeted single objects, or very small samples.

Ion-induced modifications of interstellar dust grains C. Jäger1, T. Sabri, G. Strazzulla , G. Baratta, M.E. Palumbo, E. Wendler, and Th. Henning

1 Laboratory Astrophysics Group of the Max Planck Institute for Astronomy at the Friedrich Schiller University Jena, Institute of Solid State Physics

Circumstellar and interstellar dust grains are mainly dominated by amorphous silicates and hydrogenated carbon grains. We have studied the ion-induced structural and chemical modifications of interstellar dust grains. Interstellar grains may occur as uncoated and ice-coated grains. The interaction of both types of dust with ions may lead to manifold structural and chemical modifications of grains. For instance, selective sputtering of oxygen causes the formation of metallic inclusions in silicate grains. A new and interesting field of research will be the ion-induced processes at the inter- face

between grains and ice. The erosion of carbon grains at such an interface and the formation of CO2 and CO in the ice layer on top of grains were observed upon bombardment with 200 keV H+ at 17 K. In addition, a graphitization process of the carbon beneath the ice layer was firmly detected. For comparison, the same ion bombardment of uncoated carbon layers revealed a less efficient graphitization process. The poster gives an overview on the experimental studies recently performed in the laboratory and will discuss the consequences for the dust materials and other important processes such as the interstellar chemistry in ices. The Dust Extinction Curve in the Small Magellanic Cloud from Reddened Red Clump Stars Petia Yanchulova Merica-Jones1, Karin Sandstrom1, L. Clifton Johnson1 1University of California, San Diego, USA We measure the average dust extinction curve in the southwest bar of the Small Magellanic Cloud (SMC) using multi-band Hubble Space Telescope (HST) observations of red clump stars from SMIDGE (Small Magellanic Cloud Investigation of Dust and Gas Evolution). SMC-like extinction is widely used to correct for the effects of dust in low metallicity or high redshift galaxies; however, there are currently very few extinction curve measurements in the SMC. We sample a 200 pc x 100 pc region and measure the extinction curve shape from the color-magnitude diagram (CMD) of several thousand reddened red clump stars. The slope of the vector along which these stars are reddened can theoretically directly trace the extinction curve shape. We create a model for the red clump CMD which takes into account the effects of the slope of the reddening vector, a log-normal distribution of AV, and the depth of the stellar distribution along the line of sight. Comparing our model with the observed red clump CMD we find that the observed slope is also sensitive to the line-of-sight depth. The SMIDGE photometry allows us to separate the effect due to reddening by dust and that due to an extended galactic structure and measure both the extinction curve and the line-of-sight depth. We are able to confirm an SMC-like extinction curve shape (as in Gordon et al. 2003 determined from ultraviolet spectroscopy) and a significant line-of-sight depth (as in Scowcroft et al. 2016). We demonstrate a similar effect for the Large Magellanic Cloud and compare this to the results from De Marchi et al. (2016). High-resolution, 3D radiative transfer modeling of nearby DustPedia galaxies Sam Verstocken1, Ilse De Looze2,3, Maarten Baes1 1Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, B-9000 Gent, Belgium

2Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK 3Department of Physics & Astronomy, University College London, Gower Place, London WC1E 6BT, UK

The DustPedia project aims at conducting a definitive study of interstellar dust in the Local Universe, by gathering multi-wavelength imaging data of nearby galaxies, and modelling them with state-of-the-art modeling tools. As part of the DustPedia project, we create 3D models for a representative set of nearby galaxies using the radiative transfer code SKIRT. We simultaneously derive the 3D distribution and spectral properties of the stellar populations and the interstellar dust in each galaxy, by fitting radiative transfer models directly to imaging data from UV to submm wavelengths. We fully take into account the effects of absorption, multiple scattering and thermal re-emission by the dust in our models.

We present preliminary modelling results on two well-known face-on spiral galaxies, M51 and M81, and focus on the dust heating mechanisms in these galaxies. By using radiative transfer, we take into account the effects of non-local heating, as opposed to for example pixel-by-pixel modelling techniques. We exploit our knowledge of the internal radiation field to investigate the contribution of the evolved and young stellar populations to the heating of the dust at every position in the galaxy. Our results indicate that young stellar populations are not always the dominant heating agent, and that the contribution of evolved population is important as well.

Protostellar Disk Formation Enabled by Removal of Small Dust Grains Bo Zhao1 1 MPE, Garching, Germany It has been shown that a realistic level of magnetization of dense molecular cloud cores can suppress the formation of a rotationally supported disk (RSD) through catastrophic magnetic braking in the axisymmetric ideal MHD limit. In this study, we present conditions for the formation of RSDs through non-ideal MHD effects computed self-consistently from an equilibrium chemical network. We find that removing from the standard MRN distribution the large population of very small grains (VSGs) of ~10 Å to few 100 Å that dominate the coupling of the bulk neutral matter to the magnetic field increases the ambipolar diffusivity by ~1-2 orders of magnitude at densities below 10^10 cm−3. The enhanced ambipolar diffusion (AD) in the envelope reduces the amount of magnetic flux dragged by the collapse into the circumstellar disk-forming region. Therefore, magnetic braking is weakened and more angular momentum can be retained. With continuous high angular momentum inflow, RSDs of tens of AU are able to form, survive, and even grow in size, depending on other parameters including

cosmic-ray ionization rate, magnetic field strength, and rotation speed. Some disks become self-gravitating and evolve into rings in our 2D (axisymmetric) simulations, which have the potential to fragment into (close) multiple systems in 3D. We conclude that disk formation in magnetized cores is highly sensitive to chemistry, especially to grain sizes. A moderate grain coagulation/growth to remove the large population of VSGs, either in the prestellar phase or during free-fall collapse, can greatly promote AD and help formation of tens of AU RSDs.